1. Field of the Invention
The present invention relates to a soft magnetic film used as, for example, a core layer of a thin film magnetic head. More particularly, the present invention relates to a soft magnetic film having soft magnetic characteristics of, in particular, a high resistivity xcfx81, a low coercive force Hc and a high saturation magnetic flux density Ms, to a method of manufacturing the soft magnetic film, and to a thin film magnetic head using the soft magnetic film.
2. Description of the Related Art
A magnetic head mounted on, for example, a hard disc and the like has a thin film magnetic head disposed at the extreme end of a gimbal, and the thin film magnetic film is composed of a writing inductive head and a reading MR head.
The inductive head is ordinarily composed of a lower core layer formed of a magnetic material, an upper core layer facing the lower core layer through a non-magnetic gap layer, and a coil layer for inducing a recording magnetic field to both the layers.
The upper core layer and the lower core layer have been formed of an existing magnetic material such as a Nixe2x80x94Fe alloy film (Permalloy) and the like. The Permalloy has a high permeability and a relatively high saturation magnetic flux density Ms.
However, when the recording frequency and recording density increase the Permalloy which forms the lower core layer and the upper core layer generates an eddy current because it has a low resistivity xcfx81. A thermal loss is liable to be caused by the eddy current.
An object of the present invention for solving the above problem is to provide a soft magnetic film which improves the resistivity xcfx81 while maintaining the coercive force Hc and a saturation magnetic flux density Ms in a suitable state by adding an element X (X to the Nixe2x80x94Fe alloy is one or more the group of elements selected from O (oxygen), C (carbon), N (nitrogen), and S (sulfur)) further objects of the present invention are, to provide a method of manufacturing the soft magnetic film, and to provide a thin film magnetic head capable of coping with an increase in the recording density and an increase in the recording frequency by using the soft magnetic film in core layers.
A soft magnetic film of the present invention contains at least Ni, Fe and an element X (X is one or more kinds of elements selected from O, C, N, and S) as the competition thereof, the average grain size of the soft magnetic film is 80 xc3x85 or less, and an amount of Fe is 30 percent by mass or more.
It is preferable that the average grain size be within the range of 60 xc3x85 or more to 80 xc3x85 or less.
It is preferable in the present invention that O, C, and S be contained as the composition of the soft magnetic film.
In the above case, it is preferable that the composition ratio of O+C+S, which is obtained by adding the composition ratios of O, C, and S, be 0.60 percent by mass or more to 5.00 percent by mass or less.
In the range of the above numerical values, it is preferable that the composition ratio of O is 0.40 percent by mass or more to 3.70 percent by mass or less.
It is preferable that the composition ratio of C is 0.11 percent by mass or more to 0.90 percent by mass or less.
Further, it is preferable that the composition ratio of S is 0.05 percent by mass or more to 0.43 percent by mass or less.
In the present invention, the resistivity xcfx81 of the soft magnetic film can be made to 60 xcexcxcexa9xc2x7cm or more to 210 xcexcxcexa9xc2x7cm or less by restricting the numerical values as described above.
It is more preferable that the composition ratio of O+C+S which is obtained by adding the composition ratios of O, C, and S be 1.16 percent by mass or more to 5.00 percent by mass or less.
Within the range of above numerical values, it is preferable that the composition ratio of O be 0.87 percent by mass or more to 3.70 percent by mass or less.
It is preferable that the composition ratio of C be 0.21 percent by mass or more to 0.90 percent by mass or less.
Further, it is preferable that the composition ratio of S be 0.10 percent by mass or more to 0.43 percent by mass or less.
In the present invention, the resistivity xcfx81 of the soft magnetic film can be made to 80 xcexcxcexa9xc2x7cm or more to 210 xcexcxcexa9xc2x7cm or less by restricting the numerical values as described above.
In the present invention, it is more preferable that the composition ratio of O+C+S which is obtained by adding the composition ratios of O, C, and S be 1.73 percent by mass or more to 5.00 percent by mass or less.
In the range of above numerical values, it is preferable that the composition ratio of O be 1.30 percent by mass or more to 3.70 percent by mass or less.
It is preferable that the composition ratio of C be 0.32 percent by mass or more to 0.90 percent by mass or less.
Further, it is preferable that the composition ratio of S is 0.15 percent by mass or more to 0.43 percent by mass or less.
In the present invention, the resistivity xcfx81 of the soft magnetic film can be made to 100 xcexcxcexa9xc2x7cm or more to 210 xcexcxcexa9xc2x7cm or less by restricting the numerical values as described above.
It is preferable in the present invention that the average roughness (Ra) of the centerline of the film surface of the soft magnetic film be 140 xc3x85 or less. With this arrangement, the coercive force Hc of the soft magnetic film can be made to 118.5 A/m or less.
In the present invention, it is more preferable that the average roughness (Ra) of the centerline of the film surface of the soft magnetic film be 120 xc3x85 or less. With this arrangement, the coercive force Hc of the soft magnetic film can be made to 79 A/m or less.
In the present invention, it is furthermore preferable that the average roughness (Ra) of the centerline of the film surface of the soft magnetic film be 50 xc3x85 or less. With this arrangement, the coercive force Hc of the soft magnetic film can be made to 39.5 A/m or less.
In the present invention, the saturation magnetic flux density Ms of the soft magnetic film can be made to 1.0 T or more.
It is preferable that the soft magnetic film be formed by plating.
In the present invention, it is preferable that the soft magnetic film be formed in a plating bath containing Fe ions and Ni ions to which amino organic materials are added and that the soft magnetic film contain at least Fe, Ni and the element X, which is at least one element element selected from the group of O, C, N, and S.
Further, it is preferable in the present invention that saccharin be added to the plating bath. The addition of the saccharin increases particularly the multiplier effect of the saccharin and the amino organic materials, whereby the resistivity xcfx81 can be increased because the non-metal element X such as O, C, N, S and the like is contained in the soft magnetic film. Further, it is also possible to reduce the stress of the soft magnetic film formed by the plating through the addition of the saccharin.
In the present invention, it is contemplated that SO2 contained in the saccharin enters the composition of the soft magnetic film by the addition thereof in the plating bath as described above so that S can be contained in the soft magnetic film.
In the present invention, it is preferable that the pH (index for the hydrogen ion concentration) of the plating bath be kept to 1.8 or less. The pH of the plating bath is more preferably kept to 1.7 or less and furthermore preferably to 1.5 or less.
Further, in the present invention, it is preferable that the temperature of the plating bath be kept within the range of from 20xc2x0 C. to 28xc2x0 C.
In the present invention, it is preferable that the amino organic material is at least one or material selected from the group of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), alanine (Ala) and glutamic acid (Glu).
In the present invention, when the element X wherein at least one X is elements selected from the group of O, C, N, and S is contained in the soft magnetic film composed of a Nixe2x80x94Fe alloy, the resistivity xcfx81 is improved while maintaining the coercive force Hc and the saturation magnetic flux density Ms to be substantially similar levels as those of the Nixe2x80x94Fe alloy.
Ni and Fe contained in the soft magnetic film of the present invention carry magnetism. In particular, it is preferable that the content of Fe be as large as possible to obtain a high saturation magnetic flux density Ms.
Since the element X (X is one or more element selected from O, C, N, and S) is a non-metal material, the resistivity xcfx81 of the soft magnetic film can be improved by containing the element X in the soft magnetic film. The crystal of the soft magnetic film can be miniaturized by the element X contained therein. It has been confirmed by the experiment which will be described later that when the average grain size of the soft magnetic film is made to 80 xc3x85 or less by containing the element X in a proper amount, the resistivity xcfx81 is improved as compared with that of the Nixe2x80x94Fe alloy which has been used as core layers.
In the present invention, when Fe is contained in the soft magnetic film in an amount of 30 percent by mass or more, the resistivity xcfx81 of the soft magnetic film is improved the coercive force Hc is low as that of the Nixe2x80x94Fe alloy and the saturation magnetic flux density Ms is as high as that of the Nixe2x80x94Fe alloy.
In the present invention, it is preferable that S be contained in the soft magnetic film and that the three elements of O, C, and S are contained in the soft magnetic film.
In the present invention, the relationship between contents (percent by mass) of O, S, and C and a resistivity xcfx81 is determined, thereby obtaining the proper amounts of them as explained in the experiment to be described later.
In the present invention, it has been found that a coercive force Hc cannot be always suppressed to a low level only by adjusting the contents of Fe, and the like as described above. The respective conditions of the plating bath used in the formation of the soft magnetic film must be properly adjusted to properly reduced the coercive force Hc.
In the present invention, when the amino organic materials are added to contain Fe ions and Ni ions in the plating bath and further to contain the element X (X is one or more kinds of elements selected from O, C, N, and S) in the soft magnetic film, the pH of the plating bath is reduced and specifically set to 1.8 or less. When the pH is kept as low as 1.8 or less and further the temperature of the plating bath is kept as low as 20xc2x0 C. to 28xc2x0 C., a film forming rate is delayed and the average roughness (Ra) of the centerline a formed soft magnetic film is made to 140 xc3x85 or less.
As described above, according to the present invention, it is contemplated that crystallomagnetic anisotropic energy, which influences the coercive force Hc can be weakened by setting the pH of the plating bath to 1.8 or less and by setting the average roughness (Ra) of the centerline of the formed soft magnetic film to 140 xc3x85 or less, whereby the coercive force Hc can be reliably reduced.
The magnetic head according to the present invention includes a lower core layer, an upper core layer acting as a surface facing a recording medium which faces the lower core layer through a magnetic gap, and a coil layer for inducing a recording magnetic field to both the core layers. Further, at least one of the upper core layer and the lower core layer are formed of the soft magnetic film.
As described above, in the present invention, the soft magnetic film which has a high resistivity xcfx81 and further maintains a low coercive force Hc and a high saturation magnetic flux density Ms is used as at least one of the lower core layer and the upper core layer. With this arrangement, the magnetic head which can cope with an increase in the in both instance recording density and an increase in a recording frequency may be manufactured.